Method of cleaning CVD device

ABSTRACT

A method of cleaning a CVD vacuum vessel which has an electrically conductive partition plate which divides an interior of the vacuum vessel into a plasma generating space and a film-deposition processing space, and in the electrically conductive partition plate there is a plurality of through-holes connecting the plasma generating space to the film-deposition processing space, the method includes the steps of feeding a cleaning gas into the plasma-generating space; generating active seeds by applying high-frequency electric power to electrodes arranged in the plasma-generating space; feeding the generated active species into the film-deposition processing space through the plurality of through-holes in the electrically conductive partition plate; and cleaning the film-deposition processing space by the active seeds which have been fed into this film-deposition processing space.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the priority of Japanese PatentApplication No. 2001-012600, filed in Japan on Jan. 22, 2001, the entirecontents of which are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The invention relates to a method of cleaning a chemical vapordeposition system(referred to in the present patent specification as“CVD system”).

2. Description of Related Art

It is known to use high-temperature polysilicon-type TFTs (thin-filmtransistors) and low-temperature polysilicon-type TFTs in methods ofmanufacturing liquid crystal displays.

In order to obtain high-quality oxide films in the manufacturing methodsusing high-temperature polysilicon-type TFTs, quartz substrates whichcould withstand high temperatures of 1000° C. or more are used.

In contrast, in the manufacture of low-temperature polysilicon-typeTFTs, it is necessary to carry out film deposition in a low-temperatureenvironment (for example 450° C. or less) because a glass substratewhich is customary for TFTs is used. Methods for manufacturing liquidcrystal displays using low-temperature polysilicon-type TFTs have theadvantage that they do not require special substrates to be used. Suchmethods have been put into practice in recent years and their productionvolume is continuing to expand.

In the manufacture of liquid crystal displays using low-temperaturepolysilicon-type TFTs, plasma CVD is used when a silicon oxide film isdeposited as a gate insulator film at low temperature. When siliconoxide film is deposited by plasma CVD, silane, tetraethoxysilane (TEOS)and the like are used as typical materials in gas form.

If silane, or the like, is used as the material in gas form and siliconoxide film is deposited by means of plasma, in the conventional plasmaCVD system, silicon oxide film is deposited on the surface of asubstrate by introducing the material in gas form and oxygen, or thelike, into the space in front of said substrate, generating plasma in agas mixture comprising the material in gas form and the oxygen or thelike and exposing the substrate to said plasma.

The conventional plasma CVD systems are configured in such a way thatthe material in gas form is supplied directly into the plasma which isgenerated inside the plasma CVD system. For this reason, with theconfiguration of conventional plasma CVD system, there is a problem thatthe high-energy ions are injected from the plasma present in the spacein front of the substrate onto the film-depositing face of the substrateand they damage the silicon oxide film and degrade the properties of thefilm. Furthermore, as the material in gas form is fed directly into theplasma, particles are produced by violent reaction between the materialin gas form and the plasma, and as a result the yield is reduced.

In order to solve the above mentioned problems, an attempt to improvethe CVD device of the remote plasma type is disclosed in Japan PatentApplication Serial Number H11-157692.

The CVD device disclosed in the above mentioned the patent application,Serial Number H11-157692, produces active seeds (radicals) by generatingplasma inside a vacuum vessel, carries out the film-depositionprocessing on a substrate, accommodated inside said vacuum vessel, bymeans of these active seeds and material in gas form.

That is to say, an electrically conductive partition plate which dividesthe interior of said vacuum vessel into two chambers is provided in saidvacuum vessel. The interior of one of these two chambers is formed as aplasma-generating space in which high-frequency electrode are arranged,and the interior of the other chamber is formed as a film-depositionprocessing space in which a substrate-holding mechanism on which asubstrate is mounted is arranged. A plurality of through-holes which aremade to pass from the plasma-generating space to the film-depositionprocessing space are formed in this electrically conductive partitionplate. Furthermore, this electrically conductive partition plate has aninterior space which is divided off from the plasma-generating space andcommunicates with the film-deposition processing space via a pluralityof diffusion holes. The system is configured in such a way that thematerial in gas form is supplied to the interior space of thiselectrically conductive partition plate from the outside and fed intosaid film-deposition processing space through said plurality ofdiffusion holes. The active seeds which are generated in saidplasma-generating space are fed into the film-deposition processingspace through the plurality of through-holes formed in said electricallyconductive partition plate and film processing is performed on saidsubstrate in film-deposition processing space.

In said CVD system disclosed in Patent Application Serial NumberH11-57692, the plurality of through-holes which are made to pass fromsaid plasma-generating space and are provided in said electricallyconductive partition plate to said film-deposition processing space areformed to satisfy the condition uL/D>1 when the gas flow velocity insidesaid through-holes is u, the effective length of the through-holes is Land the coefficient of mutual gas diffusion is D.

As the plasma-generating space and film-deposition processing space areseparated by means of the electrically conductive partition plate insaid CVD system proposed in Patent Application Serial Number H11-157692,the device is configured in such a way that the processing surface ofthe substrate which is arranged in the film-deposition processing spaceis not exposed to the plasma. In addition, a plurality of through-holeswhich are made to pass from the plasma-generating space tofilm-deposition processing space are formed in the electricallyconductive partition plate. However, because these through-holes areformed so as to satisfy the above_mentioned condition, the material ingas form which is fed into the film-deposition processing space isprevented from diffusing back into the plasma-generating space.

It is to be noted that in Patent Application Serial Number H11-157692, aCVD system is proposed which is formed in such a way that said pluralityof diffusion holes also fulfill the above mentioned condition placed onthe through-holes, in order to prevent the active species fed into thefilm-deposition processing space from diffusing back into the interiorspace of the partition plate.

In fact, Patent Application Serial Number H11-157692 discloses a CVDsystem in which plasma is generated between the high-frequency electrodeand the lower face part of the upper part of the vacuum vessel and inthe space which is bounded by the high-frequency electrode and thepartition wall comprised of vacuum vessel which makes up the CVD systemand the electrically conductive partition plate, both of which are atground potential. Further more, the variation of the above mentioned CVDsystem is disclosed in which, the high frequency electrodes areinstalled in upper positions in the plasma-generating space and plasmaelectrical discharge is produced between the high-frequency electrodeand the electrically conductive partition plate.

Generally, there are problems common to CVD systems that when filmscontinue to be deposited, they are also deposited on thesubstrate-supporting elements and the interior wall of thefilm-depositing chamber and the like. When they drop off onto thesubstrate during film deposition as particles, they cause to bedisconnect circuits of the wiring and result in the reduction of theyield of manufactures products.

For this reason, apart from the film-depositing process, optimumcleaning is carried out after processing the prescribed number ofsubstrates, said cleaning being performed using particular cleaninggases according to differences in the plasma-forming method andstructures and compositions of the deposited materials. The cleaning ofthis type of CVD device is an important process, as is thefilm-deposition process in the implementation of stabilized operation ofthe CVD system without exposing the interior of the depositing chamberto the atmospheric ambient.

OBJECTS AND SUMMARY

An object of the present invention is to provide an optimum cleaningprocess for the CVD system disclosed in Patent Application Serial NumberH11-157692.

In the manufacture of large liquid crystal displays in which lowtemperature polysilicon-type TFTs are used, the CVD device disclosed inPatent Application Serial Number H11-157692 uses plasma and depositssilicon oxide film on a large-area substrate using material in gas form,such as silane, in order to form at low temperatures a suitable siliconoxide film as a gate insulator film. An appropriate cleaning method isproposed which is suitable for this disclosed CVD system and a methodfor cleaning the CVD system is proposed in which the generation ofparticles is sufficiently suppressed, high manufacturing-product yieldby means of said CVD system is maintained and said CVD system_can carryout stable operations without exposing the interior of the depositingchamber to the atmospheric ambient.

A method of cleaning a CVD device according the present invention can beused in the CVD system disclosed in Patent Application Serial NumberH11-157692. According to one aspect of the present invention with anelectrically conductive partition plate placed at ground potential,cleaning gas is fed into a plasma-generating space, active species aregenerated by applying high-frequency electric power to thehigh-frequency electrodes arranged in said plasma-generating space, saidgenerated active species are fed into a film-deposition processing spacethrough a plurality of through-holes in said electrically conductivepartition plate and said film-deposition processing space is cleaned bymeans of said active species fed into this film-deposition processingspace.

That is to say, in the CVD system which is disclosed in PatentApplication Serial Number H11-157692, the plasma-generating space andthe film-deposition processing space are separated from one another byan electrically conductive partition plate and a plurality ofthrough-holes is made to pass from the plasma-generating space to thefilm-deposition processing space in said electrically conductivepartition plate. The through-holes are formed such that they fulfilconditions which prevent back-diffusion to the plasma-generating spaceside of the material in gas form fed from the film-deposition processingspace.

Cleaning gas is fed directly into the plasma-generating space, which isseparated from the film-deposition processing space by the electricallyconductive partition plate, and active species (radicals) are generatedby applying high-frequency electric power to the high-frequencyelectrode inside said plasma-generating space. The generated activespecies (radicals) are fed into the film-deposition processing spacethrough the plurality of through-holes in the electrically conductivepartition plate, which is at ground potential, and the film-depositionprocessing space is cleaned by means of the active species fed into thefilm-deposition processing space.

According to the present invention, it is possible to use fluoride gasas the cleaning gas. One or more types of the fluoride gases from suchas, for example, NF3, F2, SF6, CF4, C2F6, C3F8 can be used.

When fluoride gas is used as the cleaning gas to apply the presentinvention to the actual cleaning, after processing of a prescribednumber of silicon oxide films and a-Si films, fluoride gas is fed intothe plasma-generating space, and active species (fluorine radicals) aregenerated by striking electrical discharge in the plasma-generatingspace. The fluorine radicals are fed into the film-deposition processingspace through the plurality of through-holes in the electricallyconductive partition plate at ground potential, and the film-depositionprocessing space is cleaned. In other words, deposits attached to theinner walls of the vacuum vessel and to the surface of thesubstrate-holding mechanism, and the like, react with said fluorineradicals and thus can be removed and expelled from an exhaust port.

In this respect, oxygen gas can be added to the above mentioned fluoridegas in order to further the dissociation into the fluorine atomradicals. For example, J. Appl. Phys. Vol. 52 (1981) p. 162 proposesthat by adding oxygen with a concentration of 60% or less, it ispossible to increase the density of fluorine atom radicals in comparisonwith cases in which there is no additive.

If fluoride gas is used, as mentioned above, the radicals generatedinside the plasma-generating space are fluoride radicals or fluorineatom radicals. However, but in cases where the deposits on thefilm-processing space and the like are carbonates, O2 is used as thecleaning gas.

In addition, in cases in which the density of the plasma is low and asufficient cleaning speed is not obtained, if an inert gas with a highionization potential such as He, Ne, Ar, Kr and Xe is admixed with thecleaning gas, it is possible to raise the temperature of the electronsby the admixture of said inert gas, to further the dissociation of thecleaning gas such as fluoride gas and to increase the cleaning speed.

In cases in which the method of cleaning a CVD system according to thepresent invention is implemented using fluoride gas as the cleaning gasas mentioned above, the cleaning gas which is adsorbed in the inner faceof the through-holes, in the partition plate and on the partition plateduring the cleaning step may desorb in the progress of thefilm-depositing step after the completion of the cleaning, may bedischarged into the film-deposition processing space from the interiorof the partition plate, and fluorine which is produced due to cleaninggas may be included in the thin film during the film deposition afterthe completion of the cleaning and degrades the intrinsic properties ofthe thin film.

The present application proposes a method of cleaning a CVD systemwhich, as mentioned above, can suppress in advance the above_mentionedproblem which occurs in cases in which fluoride gas is used as thecleaning gas in the cleaning method according to the present invention.

In the method of cleaning the above_mentioned CVD system, according toone aspect of the present invention, when, with the electricallyconductive partition plate at ground potential, cleaning gas is fed intosaid plasma-generating space, active species are generated by applyinghigh-frequency electric power to the high-frequency electrode arrangedin the interior of said plasma-generating space and said generatedactive species are fed into said film-deposition processing spacethrough the plurality of through-holes in said electrically conductivepartition plate. The electrically conductive partition plate is heated,and more specifically, heating of said electrically conductive partitionplate can be carried out within a temperature range which suppresses theadsorption of fluorine onto the inner circumferential face of saidthrough-holes and the surface of the partition plate.

The temperature range at which the adsorption of fluorine onto the innercircumferential face of the through-holes and the surface of thepartition plate is prevented varies respectively depending on the typeof fluoride gas used as cleaning gas. For example, in cases in which thecleaning gas is a fluorocarbon gas such as CF4, C2F6, C3F8 and in caseswhen the cleaning gas is a nitrogen fluoride gas such as NF3 theelectrically conductive partition plate is heated to 200° C. or more,and in cases when the cleaning gas is a fluorosulfur gas such as SF6 theelectrically conductive partition plate is heated to 100° C. or more.

Such heating of the electrically conductive partition plate can becarried out, for example, by housing heating means, such as a heater, inthe electrically conductive partition plate.

With the respective cleaning method, as it is possible to heat theelectrically conductive partition plate to the necessary temperature atwhich the adsorption of cleaning gas onto the inner circumferential faceof said plurality of through-holes provided in said electricallyconductive partition plate and the surface of the partition plate isinhibitted, said heating being in accordance with the type of fluoridegas used as cleaning gas, it is possible to remove the fluorine which isabsorbed onto the inner circumferential face of the through-holes andthe surface of the partition plate during the cleaning and to prevent inadvance the fluorine contamination of the thin film during the filmdeposition of the film-depositing process after the completion ofcleaning.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a view of a vertical section showing the configuration of afirst embodiment of a CVD system in which the present invention can beapplied.

FIG. 2 is a view of a vertical section showing the configuration of asecond embodiment in which the present invention can be applied.

FIG. 3(a) is an enlarged sectional view of places where the partitionplate is fixed.

FIG. 3(b) is an enlarged sectional view of an embodiment of thepartition plate in which heating means are housed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of a CVD system in which a cleaning method according tothe present invention can be applied will be described with reference toFIGS. 1 and 2.

The CVD device shown in FIGS. 1 and 2 are preferably used when silane isemployed as the material in gas form, and silicon oxide film is formedas the gate insulator film on an upper surface of a glass substrate 11which is customary for a TFT.

When film-deposition processing is carried out in the vacuum vessel 12,the vessel interior is maintained in a desired vacuum state by means ofan exhaust device 13. The exhaust device 13 is connected to an exhaustport 12 b-1 formed in the vacuum vessel 12.

In the interior of the vacuum vessel 12, a partition plate 14, which ismade of electrically conductive material, is installed in a horizontalstate. The partition plate 14, which has a planar, for example,rectangular, shape, is arranged in such a way that its peripheral partforms a sealed state by pushing it down and attaching it to the lowerface of the electrically conductive material fixing part 22. In thisway, the interior of the vacuum vessel 12 is separated into two chambersin the upward and downward directions by the partition plate 14. Theupper chamber is made into the plasma-generating space 15, and the lowerchamber is made into the film-deposition processing space 16.

The partition plate 14 has a desired specific thickness and is entirelyin the shape of a flat plate. Furthermore, it is of planar shape similarto the shape of the horizontal section of the vacuum vessel 12. Aninterior space 24 is formed in the partition plate 14, and a pluralityof through-holes 25 which fulfill specific conditions are formed anddistributed throughout the interior space 24. The plasma-generatingspace 15 and the film-deposition processing space 16 communicate onlyvia the through-holes 25.

A glass substrate 11 is arranged on a substrate-holding mechanism 17installed in the film-deposition processing space 16. The glasssubstrate 11 is essentially parallel with the partition plate 14 and isarranged in such a way that its film-depositing face (upper face) isfacing the lower face of the partition plate 14. The potential of thesubstrate-holding mechanism 17 is kept at ground potential 41 which isthe same potential as the vacuum vessel 12. Furthermore, a heater 18 isinstalled in the substrate-holding mechanism 17. This heater 18 is usedto keep the temperature of the glass substrate 11 at a prescribedtemperature.

The vacuum vessel 12 is configured, from the point of view of improvingits assembly properties, of an upper vessel 12 a which forms theplasma-generating space 15 and a lower vessel 21 b which forms thefilm-deposition processing space 16. When the vacuum vessel 12 is formedby assembling the upper vessel 12 a and lower vessel 12 b, theelectrically conductive partition plate 14 is installed between the two.In order to ensure that it is placed at ground potential, the partitionplate 14 is mounted so as to make contact with the electricallyconductive material fixing part 22, in the manner as shown in FIG. 3(a),for example. In this way, the separated plasma-generating space 15 andfilm-deposition processing space 16 are formed on the upper and lowersides of the partition plate 14 and the plasma-generating space 15 isformed by means of the partition plate 14 and upper vessel 12 a.

In the embodiment shown in FIG. 1, the region in which plasma 19 isgenerated in the plasma-generating space 15 is formed from the partitionplate 14, upper vessel 12 a and plate-shaped electrode (high-frequencyelectrode) 20 which are arranged in an approximately central position.

A plurality of holes 20 a are formed in the electrodes 20. Theelectrodes 20 are supported and fixed by means of two insulator parts 21a, 21 b which are installed along the inner face of the side part of theupper vessel 12 a.

An is to be noted that the electrically conductive element 32 issandwiched between the partition plate 14 and the fixing part 22, whichis made of electrically conductive material and which is positionedinside the vacuum vessel 12. The partition plate is fixed to the thefixing part 22 by means of a mounting screw 33 (FIG. 3(a)). Theelectrically conductive element 32 is a cord-shaped electricallyconductive element which has spring properties in the manner of what isreferred to as a spiral shield, and it ensures electric contact betweenthe partition plate 14 and the fixing part at ground potential andabsolutely noleakage to the film-processing space of high frequencywaves. However, provided that the partition plate 14 is mounted in sucha way that it is reliably kept at ground potential when the CVD deviceis being cleaned, it is not restricted to the structure in FIG. 3(a).

In addition, the heater 30 for heating the interior partition plate 14can be accommodated in the partition plate 14 as shown in FIG. 3(b). Inthis case, a feed pipe 28 is arranged above the heater 30.

In cases in which fluoride gas is used as the cleaning gas, the heater30 is placed in such a way that the partition plate 14 is heated up toat least the necessary temperature, at which adsorption of the cleaninggas into the inner circumferential face of the plurality ofthrough-holes 25 provided in the partition plate 14 and the surface ofthe partition plate is prevented, said heating being carried out inaccordance with the type or types of fluoride gas. In this respect, thenumber of heaters 30 accommodated, and the state in which they arearranged, can be freely determined in accordance with the size of thepartition plate 14 and the necessary parameters of the heatingtemperature, and the like. In addition, it is possible to accommodate inthe partition plate 14, in the same way as the heater 30, a thermocoupledetection sensor (not shown in the figure) or the like for detecting theheating temperature of the partition plate 14.

Provided that the structure and heating means and the like for heatingthe partition plate 14 are configured so as to fulfill the aboveobjective, they are not restricted to the form shown in FIG. 3(b).

Feed pipes 23 a, 23 b, which introduce oxygen gas and cleaning gas intothe plasma-generating space 15 from the outside, are installed in aninsulator part 21 a. The oxygen gas feed pipe 23 a and cleaning gas feedpipe 23 b are connected to an oxygen gas supply and cleaning gas supply(neither shown in the figure) through a mass flow controllers whichcontrols the flow.

A fluoride gas such as NF3, F2, SF6, CF4, C2, F6, C3F8 can be used asthe cleaning gas.

In cases in which the etch rate of the cleaning gas when etching siliconoxide film is low, it is possible to add to the cleaning gas an inertgas such as He, Ne, Ar, Kr or Xe which is intended to increase theradical density by further raising the dissociation rate of the cleaninggas as a result of the rise of electron temperature of the plasma.

As the method introducing these additive gases, it is possible tocontinuously introduce these additive gases from oxygen gas feed pipe 23a, or from the gas feed pipe midway connected to the cleaning gas pipe23 b, or newly installed independent feed gas pipe exclusively providedfor the additive gases.

In the interior of the vacuum vessel 12, the plasma-generating space 15is separated from the film-deposition processing space 16 by thepartition plate 14. However, a plurality of through-holes 25, whichfulfil specific conditions, are formed in the partition plate 14 so asto penetrate the interior space 24. The plasma-generating space 15 andthe film-deposition processing space 16 communicate only via thethrough-holes 25.

Furthermore, a plurality of diffusion holes 26 which supply material ingas form to the film-processing space 16 are formed in the lower wall ofthe partition plate 14.

In order to prevent the material in gas form fed into thefilm-deposition processing space 16 from diffusing back to theplasma-generating space 15 side, the above_mentioned through-holes 25are formed so as to fulfill the condition uL/D>1 where the gas flowvelocity inside the through-holes 25 is u, the effective length of thesethrough-holes 25 is L and the coefficient of mutual gas diffusion (thecoefficient of mutual gas diffusion of two types of gas on the two sidesof the through-holes 25) is D. If said conditions which are applied tothrough-holes 25 is applied, to the diffusion-holes, @ it moreeffectively prevents the active species from diffusing back to theinterior space 24 of the partition plate 14.

A feed pipe 28 for introducing material in gas form is connected to theinterior space 24. The feed pipe 28 is arranged so as to be connectedfrom the outside. In addition, in order to ensure that the material ingas form is supplied uniformly from the diffusion holes 26, ahomogenizing plate 27, which has a plurality of holes perforatedtherein, is installed approximately horizontally in the middle of theinterior space 24.

An electric power feed rod 29, which is connected to the electrodes 20,is installed in a ceiling part of the upper vessel 12 a. High-frequencyelectric power to be discharged to the electrodes 20 is supplied by theelectric power feed rod 29. The electrodes 20 can function ashigh-frequency electrode.

The electric power feed rod 29 is covered by an insulator 31, andinsulation from other metal surface can be.

In the CVD system according to the embodiment shown in FIG. 2 thestructure of the electrodes is modified in comparison with theembodiment shown in FIG. 1, and the high-frequency electrode 20 areinstalled in a position on the upper side of the plasma-generating space15, plasma electric discharges being generated between thehigh-frequency electrodes 20 and the partition plate 14.

The basic structural elements are essentially the same as the structuralelements of the CVD system according to the embodiment presented in FIG.1 and identical reference symbols have been used for common structuralelements, hence there will not be repetition of the detailed descriptionhere.

A characteristic configuration of the embodiment shown in FIG. 2 isprovided with an insulator part 21 a on the inner side of the ceilingpart of the upper vessel 12 a, and the electrodes 20 are arranged on theunderside of said insulator part 21 a. There are no holes 20 a formed inthe electrodes 20 so that it has the shape of a single plate. Theplasma-generating space 15 is formed by the electrodes 20 and partitionplate 14, which forms a parallel plate type electrode configuration.

The rest of the configuration is essentially the same as theconfiguration of the first embodiment.

A general description will be given of the film-deposition method whichuses a cleaning method according to the invention, with respect to theCVD system configured as above. A glass substrate 11 is transferred tothe interior of the vacuum vessel 12 by means of a transferring robot(not shown in the figure), and is placed on the substrate-holdingmechanism 17. The interior of the vacuum vessel 12 is exhausted by meansof the exhaust device 13, and a prescribed vacuum state is maintained byreducing the pressure. Next, oxygen gas is fed into theplasma-generating space 15 of the vacuum vessel 12 through the oxygengas feed pipe 23 a.

A material in gas form, for example silane, is fed into the interiorspace 24 of the partition plate 14 through the feed pipe 28. The silaneis fed firstly into the upper side part of the interior space 24, it ishomogenized by the homogenizing plates 27 and moved to the lower sidepart, and next fed directly into the film-deposition processing space 16through the diffusion holes 26, i.e., without coming into contact withthe plasma. The substrate-holding mechanism 17 which is installed in thefilm-deposition processing space 16 is maintained in advance at aprescribed temperature because electricity is transmitted to the heater18.

In the state mentioned above, high-frequency electric power is suppliedto the electrodes 20 via the electric power feed rod 29. Electricdischarge is produced by means of this high-frequency electric power,and oxygen plasma 19 is generated in the vicinity of the electrode 20inside the plasma-generating space 15. By virtue of the fact that oxygenplasma 19 is generated, radicals (excited active species) which areneutral excited species are generate d, silicon oxides are deposited onthe surface of the substrate 11.

Next, a description will be given of a cleaning method according to theinvention which is applied to the above_mentioned CVD system, for thecase in which NF3 gas is used as the cleaning gas.

Cleaning is performed periodically at every preset time interval or whena preset number of substrates are processed. For cleaning, afterstopping of a material gas feeding such as silane gas, and by replacingthe oxygen gas which is introduced into the plasma generation space atfilm deposition period with fluorine gas. System configuration is notdifferent by almost same even if used cleaning gase differs.

A partition plate 14 which is formed from electrically conductivematerial is placed at ground potential, NF3 gas as cleaning gas is fedinto the plasma-generating space 15, and fluorine radicals are generatedinside the plasma-generating space 15 by supplying high-frequencyelectric power to the electrodes 20. The fluorine radicals which aregenerated are fed into the film-deposition processing space 16 throughthe plurality of through-holes 25 in the partition plate 14, and by thismeans the interior of the film-deposition processing space 16 iscleaned.

It is also possible to admix an inert gas, such as Ar gas, or oxygen gasto the cleaning gas (NF3) in order to improve the cleaning speed.

In addition, oxygen can be used as the cleaning gas in cases wherecarbonates are deposited.

In addition, in cases where fluoride gas is used as the cleaning gas,the adsorption of fluorine onto the inner circumferential face of thethrough-holes 25 and the surface of the partition plate must beprevented, and depending on the type of fluoride gas used as thecleaning gas, it is desirable to heat the partition plate 14 to 200° C.or more by means of the heater 30, when fluorocarbon gas such as CF4,C2F6, C3F8 or nitrogen fluoride gas such as NF3 are used, for example.Or, it is desirable to heat the substrate 14 to a temperature of 100° C.or more in cases when using flurosulfur gas such as SF6, while carryingout said cleaning process.

An example of specific setting values for the cleaning method for asilicon oxide film according to the present invention is given below.

Ar gas for speeding up the dissociation of cleaning gas was admixed tothe cleaning gas (NF3) with an Ar gas flow rate of 100 cm3/min (0.18g/min) under standard conditions with a power applied to the 60 MHzhigh-frequency electrodes 20 of 2 kW, and a mass flow rate, understandard conditions, of the NF3 cleaning gas of 200 cm3/min (0.63g/min). The pressure of the film-deposition processing space 16 was 16Pa. The speed with which the silicon oxide in the film-depositionprocessing space 16 was removed, in other words the cleaning speed, was30 to 40 nm/min.

As has been made clear in the description above, by means of the presentinvention, it is possible to provide an optimum cleaning method for asystem which can deposit silicon oxide film and the like on a large-areasubstrate using a material in gas form such as silane by means of plasmaCVD, in which CVD system, for example, the interior of the vacuum vesselis divided into a plasma-generating space and a film-depositionprocessing space by the position of an electrically conductive partitionplate with a plurality of through-holes or diffusion holes formedtherein, and active species are generated in the plasma-generating spaceand are fed into the film-deposition processing space through aplurality of holes in said partition plate.

With the cleaning method according to the present invention, byperforming optimum cleaning after film-deposition, the generation ofparticles can be reduced and the CVD system of the present formconfiguration can be used efficiently in the manufacture of large-areasubstrates without interpret due to exposing the interior of thedepositing chamber to the atmospheric ambient for cleaning, and yetthere is no product contamination due to fluorines caused by thecleaning gas, and it is possible to operate continuously in a stabilizedfashion without interpret due to exposing the interior of the depositingchamber to the atmospheric ambient for cleaning, which results in a highyield.

Although only preferred embodiments are specifically illustrated anddescribed herein, it will be appreciated that many modifications andvariations of the present invention are possible in light of the aboveteachings and within the purview of the appended claims withoutdeparting from the spirit and intended scope of the invention.

What is claimed is:
 1. A method of cleaning a CVD vacuum vessel whichhas an electrically conductive partition plate which divides an interiorof the vacuum vessel into a plasma generating space and afilm-deposition processing space, and in the electrically conductivepartition plate there is a plurality of through-holes connecting theplasma generating space to the film-deposition processing space, themethod comprising the steps of: feeding a cleaning gas into theplasma-generating space; generating active seeds by applyinghigh-frequency electric power to electrodes arranged in theplasma-generating space; feeding the generated active species into thefilm-deposition processing space through the plurality of through-holesin the electrically conductive partition plate; heating saidelectrically conductive partition plate; and cleaning thefilm-deposition processing space by the active seeds which have been fedinto this film-deposition processing space.
 2. The method of claim 1,further comprising the step of maintaining the electrically conductivepartition plate at ground potential.
 3. The method of claim 1, whereinthe cleaning gas is one or more types of fluoride gas.
 4. The method ofclaim 3, wherein the fluoride gases are NF₃, F₂, SF₆, CF₄, C₂F₆ andC₃F₈.
 5. The method of claim 1, further comprising the step of addingoxygen gas to the cleaning gas.
 6. The method of claim 5, wherein anamount of oxygen gas added is such that the concentration is 60% orless.
 7. The method of claim 1, wherein the cleaning gas is O₂.
 8. Themethod of claim 1, further comprising the step of adding any of He, Ne,Ar, Kr and Xe to the cleaning gas.
 9. The method of claim 1, wherein theheating of said electrically conductive partition plate is carried outwithin a temperature range which inhibits the adsorption of fluorineonto an inner circumferential face of the through-holes and the surfaceof the partition plate.
 10. The method of claim 9, wherein the cleaninggas is carbon fluoride gas or nitrogen fluoride and the electricallyconductive partition plate is heated to 200° C. or more.
 11. The methodof claim 9, wherein the cleaning gas is sulfur fluoride gas and theelectrically conductive partition plate is heated to 100° C. or more.12. A method of cleaning a CVD system, the CVD system having a vacuumvessel and a substrate accommodated in the vacuum vessel wherein theinterior of said vacuum vessel is divided into a plasma generating spaceand a film deposition processing space by an electrically conductivepartition plate, said plate comprising a plurality of through-holes thecleaning method comprising the steps of: maintaining the electricallyconductive partition plate at ground potential; feeding a cleaning gasinto the plasma-generating space; generating active seeds by applyinghigh-frequency electric power to electrodes arranged in theplasma-generating space; feeding the generated active seeds into thefilm-deposition processing space through the plurality of through-holesin the electrically conductive partition plate; heating saidelectrically conductive partition plate: and cleaning thefilm-deposition processing space by the active species which are fedinto this film-deposition processing space.
 13. The method of claim 12,wherein the cleaning gas is one or more types of fluoride gas.
 14. Themethod of claim 13, wherein the fluoride gases are NF₃, F₂, SF₆, CF₄,C₂F₆ and C₃F₈.
 15. The method of claim 12, further comprising the stepof adding oxygen gas to the cleaning gas.
 16. The method of claim 15,wherein an amount of oxygen gas added is such that the concentration is60% or less.
 17. The method of claim 12, wherein the cleaning gas is O₂.18. The method of claim 12, further comprising the step of adding any ofHe, Ne, Ar, Kr and Xe to the cleaning gas.
 19. The method of claim 12,wherein the heating of said electrically conductive partition plate iscarried out within a temperature range which inhibits the adsorption offluorine onto the inner circumferential face of said through-holes andthe surface of the partition plate.
 20. The method of claim 19, whereinthe cleaning gas is carbon fluoride gas or nitrogen fluoride and theelectrically conductive partition plate is heated to 200° C. or more.